NOS2 and Alzheimer disease: In microglia challenged with extrinsic and intrinsic toxic stimuli, there is an elevated expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2), and secretion of inflammatory mediators such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), which can stimulate neurons to cause degeneration, ultimately leading to AD.